I have indeed seen codebases where it seems like the programmer was being charged per source code byte. Full of single letter methods and such - it takes a large confusion of ideas to motivate such a philosophy.
Not at all. Brevity (or verbosity) is largely orthogonal to level of entropy or redundancy. In principle it ought to be possible to code at a higher level of abstraction while still using understandable names and control flow constructs.
I’m really not sure about that. By definition, high entropy means high information density (information per character). So with the same amount of information you would have less characters.
Think in terms of information density per symbol on the abstract syntax tree, not per character in the source code.